Electrocaloric heat transfer modular stack

ABSTRACT

A heat transfer system is disclosed including a plurality of modules arranged in a stack. The stack modules include electrocaloric element and electrodes on each side of the film. A fluid flow path is disposed between two or more electrocaloric elements. A first electrical bus element (18) in electrical contact with the first electrode (14), and a second electrical bus element (20) in electrical contact with second electrode (16). The first electrical bus element is electrically connected to at least one other electrical bus of another electrocaloric element in the stack at the same polarity as said first electrical bus, or the second electrical bus element is electrically connected to at least one other electrical bus of another electrocaloric element in the stack at the same polarity as said second electrical bus.

BACKGROUND

A wide variety of technologies exist for cooling applications, includingbut not limited to evaporative cooling, convective cooling, or solidstate cooling such as electrothermic cooling. One of the most prevalenttechnologies in use for residential and commercial refrigeration and airconditioning is the vapor compression refrigerant heat transfer loop.These loops typically circulate a refrigerant having appropriatethermodynamic properties through a loop that comprises a compressor, aheat rejection heat exchanger (i.e., heat exchanger condenser), anexpansion device and a heat absorption heat exchanger (i.e., heatexchanger evaporator). Vapor compression refrigerant loops effectivelyprovide cooling and refrigeration in a variety of settings, and in somesituations can be run in reverse as a heat pump. However, many of therefrigerants can present environmental hazards such as ozone depletingpotential (ODP) or global warming potential (GWP), or can be toxic orflammable. Additionally, vapor compression refrigerant loops can beimpractical or disadvantageous in environments lacking a ready source ofpower sufficient to drive the mechanical compressor in the refrigerantloop. For example, in an electric vehicle, the power demand of an airconditioning compressor can result in a significantly shortened vehiclebattery life or driving range. Similarly, the weight and powerrequirements of the compressor can be problematic in various portablecooling applications.

Accordingly, there has been interest in developing cooling technologiesas alternatives to vapor compression refrigerant loops. Varioustechnologies have been proposed such as field-active heat or electriccurrent-responsive heat transfer systems relying on materials such aselectrocaloric materials, magnetocaloric materials, or thermoelectricmaterials. However, many proposals have been configured as bench-scaledemonstrations with limited capabilities for scalability or massproduction.

BRIEF DESCRIPTION

In some embodiments of this disclosure, a heat transfer system comprisesa plurality of modules arranged in a stack. The stack modules comprisean electrocaloric element comprising an electrocaloric film. A firstelectrode is disposed on a first side of the electrocaloric film, and asecond electrode is disposed on a second side of the electrocaloricfilm. A fluid flow path is disposed between two or more electrocaloricelements. A first electrical bus element in electrical contact with thefirst electrode, and a second electrical bus element in electricalcontact with second electrode. The first electrical bus element iselectrically connected to at least one other electrical bus of anotherelectrocaloric element in the stack at the same polarity as said firstelectrical bus, or the second electrical bus element is electricallyconnected to at least one other electrical bus of another electrocaloricelement in the stack at the same polarity as said second electrical bus.

The first electrical bus element is electrically connected to at leastone other electrical bus of another electrocaloric element in the stackat the same polarity as said first electrical bus, and the secondelectrical bus element is electrically connected to at least one otherelectrical bus of another electrocaloric element in the stack at thesame polarity as said second electrical bus.

In any of the foregoing embodiments, the first or second electrical busis electrically connected to an electrical bus of an adjacentelectrocaloric element in the stack at the same polarity as said firstor second electrical bus.

In any of the foregoing embodiments, the first and second electrical buselements are each electrically connected to electrical bus elements ofan adjacent electrocaloric element in the stack at the same polaritiesas said first and second electrical bus elements, respectively.

In any of the foregoing embodiments, the first or second electrical buselement is in an interlocking configuration with an electrical bus of anadjacent electrocaloric element in the stack.

In any of the foregoing embodiments, the first and second electrical buselements are each in an interlocking configuration to electrical buselements of an adjacent electrocaloric element in the stack.

In any of the foregoing embodiments, the first electrical bus element iselectrically connected to a live electrode and the second electrical buselement is electrically connected to a ground electrode.

In any of the foregoing embodiments, the first and second electrical buselements are disposed along opposite edges of the electrocaloricelement.

In any of the foregoing embodiments, the first electrode extends fromthe first electrical bus element along the first side of theelectrocaloric film to a position physically separated from the secondelectrical bus element, and the second electrode extends from the secondelectrical bus element along the second side of the electrocaloric filmto a position physically separated from the first electrical buselement.

In any of the foregoing embodiments, the first and second electrical buselements are disposed along a common edge of the electrocaloric element.

In any of the foregoing embodiments, at least two adjacentelectrocaloric elements that share an electrode are at least partiallyembedded between the electrocaloric films of the adjacent electrocaloricelements.

In any of the foregoing embodiments, the embedded electrode is a liveelectrode, and comprising ground electrodes adjacent to the fluid flowpath.

In any of the foregoing embodiments, one or more spacer elements aredisposed between electrocaloric elements.

In any of the foregoing embodiments, the one or more spacer elementsextend axially along a direction of fluid flow along the fluid flowpath.

In any of the foregoing embodiments, the one or more axially-extendingspacer elements extend linearly along a direction of fluid flow alongthe fluid flow path.

In any of the foregoing embodiments, the one or more axially-extendingspacer elements extend non-linearly along a direction of fluid flowalong the fluid flow path.

In any of the foregoing embodiments, the one or more spacer elements areelectrically non-conductive.

In any of the foregoing embodiments, the electrocaloric elementthickness is 1 μm to 1000 μm.

In any of the foregoing embodiments, the physical separation betweenelectrocaloric elements in adjacent modules is from 1 μm to 200 mm.

In any of the foregoing embodiments, the plurality of modules furthercomprise an electrically non-conductive support member connected to theelectrocaloric element.

In any of the foregoing embodiments, the support includes header spacesat opposing ends of the electrocaloric elements in fluid communicationwith the fluid flow path.

In any of the foregoing embodiments, the supports of the plurality ofmodules together form an enclosure within which the electrocaloricelements and the spacer elements are disposed.

In any of the foregoing embodiments, the electrocaloric film comprisesan electrocaloric polymer.

In any of the foregoing embodiments, the electrocaloric polymercomprises polyvinylidene fluoride (PVDF) or a liquid crystal polymer(LCP),

In any of the foregoing embodiments, the electrocaloric film comprisesan inorganic electrocaloric material.

In any of the foregoing embodiments, the first and second electrodeseach comprise a metalized layer deposited on the electrocaloric film.

In some embodiments, a heat transfer system comprises an electrocaloricelement formed by the method of any of the above embodiments, a firstthermal flow path between the electrocaloric element and a heat sink, asecond thermal flow path between the electrocaloric element and a heatsource, and a controller configured to control electrical current to theconductive layers and to selectively direct transfer of heat energy fromthe electrocaloric element to the heat sink along the first thermal flowpath or from the heat source to the electrocaloric element along thesecond thermal flow path.

In another aspect, a method of fabricating the heat transfer system ofany of the foregoing embodiments comprises assembling repeating units ofthe modules in a stack configuration.

BRIEF DESCRIPTION OF THE DRAWINGS

Subject matter of this disclosure is particularly pointed out anddistinctly claimed in the claims at the conclusion of the specification.The foregoing and other features, and advantages of the presentdisclosure are apparent from the following detailed description taken inconjunction with the accompanying drawings in which:

FIG. 1 is a schematic depiction of a top view of an example embodimentof an electrocaloric heat transfer module;

FIG. 2 is a schematic depiction of a cross-section side view of anexample embodiment of an electrocaloric heat transfer module;

FIG. 3A is a schematic depiction of an exploded perspective view of anelectrode and electrocaloric film configuration;

FIG. 3B is a top view of a portion of the configuration of FIG. 4 withan electric bus element:

FIG. 4 is a schematic depiction of an example embodiment of a stackassembly of a number of electrocaloric heat transfer modules;

FIG. 5 is a schematic depiction of an alternate example embodiment of astack assembly of a number of electrocaloric heat transfer modules and

FIG. 6 is a schematic depiction of an example embodiment of heattransfer system comprising an electrocaloric stack and other components.

DETAILED DESCRIPTION

As mentioned above, a heat transfer system is disclosed that comprises aplurality of modules arranged in a stack. An example of an embodiment ofa module is schematically depicted in FIGS. 1 and 2. Although anydirections described herein (e.g., “up”, “down”, “top”, “bottom”,“left”, “right”, “over”, “under”, etc.) are considered to be arbitraryand to not have any absolute meaning but only a meaning relative toother directions, FIG. 1 can be described as a “top” view of an exampleembodiment of a module and FIG. 2 can be described as a “side”cross-section view taken along the line A4↔A shown in FIG. 1. As shownin FIGS. 1 and 2, a module 10 comprises an electrocaloric elementcomprises an electrocaloric film 12, a first electrode 14 on a firstside of the film and a second electrode 16 on a second side of the film.It is noted that, for ease of illustration so that details of theelectrocaloric film 12 and other components are not obscured, theelectrodes 14, 16 are omitted from FIG. 1 and are only illustrated inFIG. 2.

The electrocaloric film 12 can comprise any of a number ofelectrocaloric materials. In some embodiments, electrocaloric filmthickness can be in a range from having a lower limit of 0.1 μm, morespecifically 0.5 μm, and even more specifically 1 μm. In someembodiments, the film thickness range can and having an upper limit of1000 μm, more specifically 100 μm, and even more specifically 10 μm. Itis understood that these upper and lower range limits can beindependently combined to disclose a number of different possibleranges. Examples of electrocaloric materials for the electrocaloric filmcan include but are not limited to inorganic materials (e.g., ceramics),electrocaloric polymers, and polymer/ceramic composites. Examples ofinorganics include but are not limited to PbTiO₃ (“PT”),Pb(Mg_(1/3)Nb_(2/3))O₃ (“PMN”), PMN-PT, LiTaO₃, barium strontiumtitanate (BST) or PZT (lead, zirconium, titanium, oxygen). Examples ofelectrocaloric polymers include, but are not limited to ferroelectricpolymers, liquid crystal polymers, and liquid crystal elastomers.

Ferroelectric polymers are crystalline polymers, or polymers with a highdegree of crystallinity, where the crystalline alignment of polymerchains into lamellae and/or spherulite structures can be modified byapplication of an electric field. Such characteristics can be providedby polar structures integrated into the polymer backbone or appended tothe polymer backbone with a fixed orientation to the backbone. Examplesof ferroelectric polymers include polyvinylidene fluoride (PVDF),polytriethylene fluoride, odd-numbered nylon, copolymers containingrepeat units derived from vinylidene fluoride, and copolymers containingrepeat units derived from triethylene fluoride. Polyvinylidene fluorideand copolymers containing repeat units derived from vinylidene fluoridehave been widely studied for their ferroelectric and electrocaloricproperties. Examples of vinylidene fluoride-containing copolymersinclude copolymers with methyl methacrylate, and copolymers with one ormore halogenated co-monomers including but not limited totrifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene,trichloroethylene, vinylidene chloride, vinyl chloride, and otherhalogenated unsaturated monomers.

Liquid crystal polymers, or polymer liquid crystals comprise polymermolecules that include mesogenic groups. Mesogenic molecular structuresare well-known, and are often described as rod-like or disk-likemolecular structures having electron density orientations that produce adipole moment in response to an external field such as an externalelectric field. Liquid crystal polymers typically comprise numerousmesogenic groups connected by non-mesogenic molecular structures. Thenon-mesogenic connecting structures and their connection, placement andspacing in the polymer molecule along with mesogenic structures areimportant in providing the fluid deformable response to the externalfield. Typically, the connecting structures provide stiffness low enoughso that molecular realignment is induced by application of the externalfield, and high enough to provide the characteristics of a polymer whenthe external field is not applied.

In some exemplary embodiments, a liquid crystal polymer can haverod-like mesogenic structures in the polymer backbone separated bynon-mesogenic spacer groups having flexibility to allow for re-orderingof the mesogenic groups in response to an external field. Such polymersare also known as main-chain liquid crystal polymers. In some exemplaryembodiments, a liquid crystal polymer can have rod-like mesogenicstructures attached as side groups attached to the polymer backbone.Such polymers are also known as side-chain liquid crystal polymers.

With continued reference to FIGS. 1 and 2, first electrode 14 iselectrically connected to a first electrical bus element 18. Similarly,second electrode 16 is electrically connected to second electrical buselement 20. The electrodes can be any type of conductive material,including but not limited to metallized layers of a conductive metalsuch as aluminum or copper, or other conductive materials such as carbon(e.g., carbon nanotubes, graphene, or other conductive carbon). Noblemetals can also be used, but are not required. Other conductivematerials such as a doped semiconductor, ceramic, or polymer, orconductive polymers can also be used. In some embodiments, theelectrical bus elements 18 and 20 of opposite polarity are disposed onopposite edges of the electrocaloric film 12 as shown in FIG. 2, whichcan in some embodiments provide a physical separation that can reducethe risk of short circuits. As also shown in FIG. 2, the electrodes 14and 16 can extend from a position in contact with an electrical buselement on one edge of the film and extend across the film to a positionthat is not in contact with the electrical bus element of oppositepolarity on the other edge of the film 12. In some embodiments, theelectrical bus elements 18 and 20 can be disposed on the same side ofthe electrocaloric element as shown in FIGS. 3A and 3B. FIG. 3A is aschematic depiction of a perspective exploded view of an electrocaloricfilm 12 having a top electrode 14 and a bottom electrode 16. The top andbottom electrodes in FIGS. 3A and 3B have lead portions 14 y and 16 yfor an electrical connection to an electrical bus element 19. Theconnection between the electrodes 14, 16 and the bus element 19 isdepicted in a top view in FIG. 3B where only a portion of electrocaloricfilm 12 and the bus element 19 are shown. As shown in FIG. 3B, buselement has a first polarity portion 19 a connected to the lead portion14 y of top electrode 14 and a second polarity portion 19 b connected tothe lead portion 16 y of bottom electrode 16, and an electricallynon-conductive portion 19 c that electrically isolates the portions 19 aand 19 b of different polarities.

One or more support elements 22 can optionally be included for supportand retention of the electrocaloric element. However, separate supportelements are not required, as support and retention can also be providedby the bus elements as shown in FIG. 4 described below. As shown in FIG.1, the support element(s) 22 can be configured to provide header spaces24 and 26 for transport of working fluids to and from the electrocaloricelement along fluid flow path 25. Although not required in all designconfigurations, in some embodiments, the support elements can be madefrom an electrically non-conductive material.

Spacer elements 28 can optionally be included to help maintainseparation from adjacent electrocaloric elements for a fluid flow pathfor a working fluid (e.g., either a fluid to be heated or cooleddirectly such as air, or a heat transfer fluid such as a dielectricorganic compound). Any configuration of spacer elements can be utilized,such as a set of discrete disk spacer elements. In some aspects,however, the spacer elements extend axially in a direction parallel tothe direction of the fluid flow path 25. Such axial extension can belinear (i.e., in a straight line) as shown in FIG. 1, or can benon-linear (e.g., in a zig-zag or wavy pattern that extends generally inan axial direction. In some embodiments, the non-linearity can promotegood fluid mixing while the general extension in the axial direction canhelp avoid excessive back-pressure to the flowing fluid.

Turning now to FIG. 4 where like numbering is used as FIGS. 1 and 2, anumber of modules 10 are shown assembled together in a stack 30. As canbe seen in FIG. 3, the spacers promote maintaining a physical separationbetween adjacent electrocaloric elements to provide a fluid flow path 25between the spacers and the adjacent electrocaloric elements. Althoughnot required in all design configurations, in design configurationswhere the spacer elements are disposed adjacent to electrodes ofopposite polarity as shown in FIG. 3, the spacer elements can be madefrom an electrically non-conductive material. In some embodiments,spacing between adjacent electrocaloric elements can be in a range fromhaving a lower limit of 1 μm, more specifically 10 μm, and even morespecifically 50 μm. In some embodiments, the separation spacing rangecan have an upper limit of 200 mm, more specifically 10 mm, even morespecifically 2 mm. It is understood that these upper and lower rangelimits can be independently combined to disclose a number of differentpossible ranges.

In some embodiments, adjacent electrical bus elements 18, 20 can have aninterlocking configuration as shown in FIG. 4. As used herein,interlocking means that adjacent elements have complementary contour ofprojections and recesses where a projection of one bus element projectsis adjacent or projects into to a complementary recess of an adjacentbus element. Such an arrangement can in some embodiments facilitateassembly and promote structural integrity and electrical continuity ofthe assembled bus elements in the stack.

FIG. 4 depicts a stack with alternating electrocaloric elements andfluid flow passages; however, FIG. 4 represents only one example of astack embodiment and is not limiting. An alternate embodiment isdepicted in FIG. 5. With reference now to FIG. 5, a stack 30 a is shownwhere bus elements 18 b are connected to a bus bar 18 a and bus elements20 b are connected to a bus bar 20 a. As shown in FIG. 5 the electrodes16 a electrically connected to bus elements 20 b are at least partiallyembedded between the electrocaloric films 12 of adjacent electrocaloricelements. In this embodiment, the electrode 16 a serves as an electrodefor two adjacent electrocaloric elements or, put another way, the twoadjacent electrocaloric elements share a single electrode. Theelectrodes 14 a of opposite polarity are disposed on the outside of theelectrocaloric element ‘sandwich’ and are not shared. This configurationcan provide technical benefits by protecting the embedded electrode 16 afrom potential short circuits. In some embodiments, the at leastpartially embedded electrode is a live electrode, and the electrodeexposed to the fluid flow path 25 is a ground electrode. It should benoted that although FIG. 5 depicts a sandwich of two films surroundingthe embedded electrode, sandwiches of more than two films with embeddedelectrodes of alternating polarities are also contemplated.

An example embodiment of a heat transfer system and its operation arefurther described with respect to FIG. 6. As shown in FIG. 6, a heattransfer system 310 comprises an electrocaloric stack 311 has one ormore electrically conductive liquids in thermal communication with aheat sink 317 through a first thermal flow path 318, and in thermalcommunication with a heat source 320 through a second thermal flow path322. A controller 324 is configured to control electrical current tothrough a power source (not shown) to selectively activateelectrocaloric elements (not shown) in the stack 311. The controller 324is also configured to open and close control valves 326 and 328 toselectively direct the electrically conductive liquid along the firstand second flow paths 318 and 322.

In operation, the system 310 can be operated by the controller 324applying an electric field as a voltage differential across theelectrocaloric elements in the stack 311 to cause a decrease in entropyand a release of heat energy by the electrocaloric elements. Thecontroller 324 opens the control valve 326 to transfer at least aportion of the released heat energy along flow path 318 to heat sink317. This transfer of heat can occur after the temperature of theelectrocaloric elements has risen to a threshold temperature. In someembodiments, heat transfer to the heat sink 317 is begun as soon as thetemperature of the electrocaloric elements increases to be about equalto the temperature of the heat sink 317. After application of theelectric field for a time to induce a desired release and transfer ofheat energy from the electrocaloric elements to the heat sink 317, theelectric field can be removed. Removal of the electric field causes anincrease in entropy and a decrease in heat energy of the electrocaloricelements. This decrease in heat energy manifests as a reduction intemperature of the electrocaloric elements to a temperature below thatof the heat source 320. The controller 324 closes control valve 326 toterminate flow along flow path 318, and opens control device 328 totransfer heat energy from the heat source 320 to the colderelectrocaloric elements.

In some embodiments, for example where a heat transfer system isutilized to maintain a temperature in a conditioned space or thermaltarget, the electric field can be applied to the electrocaloric elementsto increase its temperature until the temperature of the electrocaloricelement reaches a first threshold. After the first temperaturethreshold, the controller 324 opens control valve 326 to transfer heatfrom the electrocaloric elements to the heat sink 317 until a secondtemperature threshold is reached. The electric field can continue to beapplied during all or a portion of the time period between the first andsecond temperature thresholds, and is then removed to reduce thetemperature of the electrocaloric elements until a third temperaturethreshold is reached. The controller 324 then closes control valve 326to terminate heat flow transfer along heat flow path 318, and openscontrol valve 328 to transfer heat from the heat source 320 to theelectrocaloric elements. The above steps can be optionally repeateduntil a target temperature of the conditioned space or thermal target(which can be either the heat source or the heat sink) is reached.

While the present disclosure has been described in detail in connectionwith only a limited number of embodiments, it should be readilyunderstood that the present disclosure is not limited to such disclosedembodiments. Rather, the present disclosure can be modified toincorporate any number of variations, alterations, substitutions orequivalent arrangements not heretofore described, but which arecommensurate with the spirit and scope of the present disclosure.Additionally, while various embodiments of the present disclosure havebeen described, it is to be understood that aspects of the presentdisclosure may include only some of the described embodiments.Accordingly, the present disclosure is not to be seen as limited by theforegoing description, but is only limited by the scope of the appendedclaims.

1. A heat transfer system, comprising a plurality of modules arranged ina stack, each of the modules comprising an electrocaloric elementcomprising an electrocaloric film, a first electrode on a first side ofthe electrocaloric film, and a second electrode on a second side of theelectrocaloric film; a fluid flow path between two or moreelectrocaloric elements; a first electrical bus element in electricalcontact with the first electrode; and a second electrical bus element inelectrical contact with second electrode; wherein the first electricalbus element is electrically connected to at least one other electricalbus of another electrocaloric element in the stack at the same polarityas said first electrical bus, or the second electrical bus element iselectrically connected to at least one other electrical bus of anotherelectrocaloric element in the stack at the same polarity as said secondelectrical bus.
 2. The heat transfer system of claim 1, wherein thefirst electrical bus element is electrically connected to at least oneother electrical bus of another electrocaloric element in the stack atthe same polarity as said first electrical bus, and the secondelectrical bus element is electrically connected to at least one otherelectrical bus of another electrocaloric element in the stack at thesame polarity as said second electrical bus.
 3. The heat transfer systemof claim 1, wherein the first or second electrical bus is electricallyconnected to an electrical bus of an adjacent electrocaloric element inthe stack at the same polarity as said first or second electrical bus.4. The heat transfer system of claims 1, wherein the first and secondelectrical bus elements are each electrically connected to electricalbus elements of an adjacent electrocaloric element in the stack at thesame polarities as said first and second electrical bus elements,respectively.
 5. The heat transfer system of claim 1, wherein the firstelectrical bus element is in an interlocking configuration with anelectrical bus of an adjacent electrocaloric element in the stack, orthe second electrical bus element is in an interlocking configurationwith an electrical bus of an adjacent electrocaloric element in thestack, or the first electrical bus element and the second electrical buselement are each in an interlocking configuration with an electrical busof an adjacent electrocaloric element in the stack.
 6. (canceled)
 7. Theheat transfer system of claim 1, wherein the first electrical buselement is electrically connected to a live electrode and the secondelectrical bus element is electrically connected to a ground electrode.8. The heat transfer system of claim 1, wherein the first and secondelectrical bus elements are disposed along opposite edges of theelectrocaloric element.
 9. The heat transfer system of claim 8, whereinthe first electrode extends from the first electrical bus element alongthe first side of the electrocaloric film to a position physicallyseparated from the second electrical bus element, and the secondelectrode extends from the second electrical bus element along thesecond side of the electrocaloric film to a position physicallyseparated from the first electrical bus element.
 10. The heat transfersystem of claim 1, wherein the first and second electrical bus elementsare disposed along a common edge of the electrocaloric element.
 11. Theheat transfer system of claim 1, comprising at least two adjacentelectrocaloric elements that share an electrode at least partiallyembedded between the electrocaloric films of the adjacent electrocaloricelements.
 12. The heat transfer system of claim 11, wherein the embeddedelectrode is a live electrode, and comprising ground electrodes adjacentto the fluid flow path.
 13. The heat transfer system of claim 1, furthercomprising one or more spacer elements between electrocaloric elements.14. The heat transfer system of claim 13, wherein the one or more spacerelements extend axially along a direction of fluid flow along the fluidflow path or wherein the one or more axially-extending spacer elementsextend linearly along a direction of fluid flow along the fluid flowpath, or wherein the one or more axially-extending spacer elementsextend non-linearly along a direction of fluid flow along the fluid flowpath.
 15. (canceled)
 16. (canceled)
 17. The heat transfer system ofclaim 13, wherein the one or more spacer elements are electricallynon-conductive.
 18. (canceled)
 19. (canceled)
 20. The heat transfersystem of claim 1, wherein said plurality of modules further comprise anelectrically non-conductive support member connected to theelectrocaloric element.
 21. The heat transfer system of claim 20,wherein the support includes header spaces at opposing ends of theelectrocaloric elements in fluid communication with the fluid flow path.22. The heat transfer system of claim 20, wherein the supports of theplurality of modules together form an enclosure within which theelectrocaloric elements and the spacer elements are disposed. 23.(canceled)
 24. (canceled)
 25. (canceled)
 26. The heat transfer system ofclaim 1, wherein the first and second electrodes each comprise ametalized layer deposited on the electrocaloric film.
 27. The heattransfer system of claim 1, further comprising a first thermal flow pathbetween the fluid flow path and a heat sink a second thermal flow pathbetween the fluid flow path and a heat source; and a controllerconfigured to control electrical current to the electrodes and toselectively direct transfer of heat energy from the fluid flow path inthermal communication with electrocaloric element to the heat sink alongthe first thermal flow path or from the heat source to the fluid flowpath in thermal communication with the electrocaloric element along thesecond thermal flow path.
 28. A method of fabricating the heat transfersystem claim 1, comprising assembling repeating units of said modules ina stack configuration.